The ability to reduce the surface tension of water is of great importance in waterborne coatings, inks, adhesives, and agricultural formulations because decreased surface tension translates to enhanced substrate wetting in actual formulations. Surface tension reduction in water-based systems is generally achieved through the addition of surfactants. Performance attributes resulting from the addition of surfactants include enhanced surface coverage, fewer defects, and more uniform distribution. Equilibrium surface tension performance is important when the system is at rest. However, the ability to reduce surface tension under dynamic conditions is of great importance in applications where high surface creation rates are utilized. Such applications include spraying of coatings or agricultural formulations, or high speed gravure or ink-jet printing. Dynamic surface tension is a fundamental quantity which provides a measure of the ability of a surfactant to reduce surface tension and provide wetting under such high speed application conditions.
Traditional nonionic surfactants such as alkylphenol or alcohol ethoxylates, and ethylene oxide (EO) propylene oxide (PO) copolymers have excellent equilibrium surface tension performance but are generally characterized as having poor dynamic surface tension reduction. In contrast, certain anionic surfactants such as sodium dialkyl sulfosuccinates can provide good dynamic results, but these are very foamy and impart water sensitivity to the finished coating.
The objective of this invention is to provide a family of surfactants which provide good equilibrium and dynamic surface tension properties and are low-foaming.
The importance of reducing equilibrium and dynamic surface tension in applications such as coatings, inks, and agricultural formulations is well-appreciated in the art.
Low dynamic surface tension is of great importance in the application of waterborne coatings. In an article, [Schwartz, J. "The Importance of Low Dynamic Surface Tension in Waterborne Coatings", Journal of Coatings Technology, September 1992] there is a discussion of surface tension properties in waterborne coatings and a discussion of dynamic surface tension in such coatings. Equilibrium and dynamic surface tension were evaluated for several surface active agents including the ethylene oxide adducts of acetylenic glycols. It is pointed out that low dynamic surface tension is an important factor in achieving superior film formation in waterborne coatings. Dynamic coating application methods require surfactants with low dynamic surface tensions in order to prevent defects such as retraction, craters, and foam.
Efficient application of agricultural products is also highly dependent on the dynamic surface tension properties of the formulation. In an article, [Wirth, W.; Storp, S.; Jacobsen, W. "Mechanisms Controlling Leaf Retention of Agricultural Spray Solutions"; Pestic. Sci. 1991, 33, 411-420], the relationship between the dynamic surface tension of agricultural formulations and the ability of these formulations to be retained on a leaf was studied. These workers observed a good correlation between retention values and dynamic surface tension, with more effective retention of formulations exhibiting low dynamic surface tension.
Low dynamic surface tension is also important in high-speed printing as discussed in the article "Using Surfactants to Formulate VOC Compliant Waterbased Inks" [Medina, S. W.; Sutovich, M. N. Am. Ink Maker 1994, 72 (2), 32-38]. In this article, it is stated that equilibrium surface tensions (EST's) are pertinent only to ink systems at rest. EST values, however, are not good indicators of performance in the dynamic, high speed printing environment under which the ink is used. Dynamic surface tension is a more appropriate property. This dynamic measurement is an indicator of the ability of the surfactant to migrate to a newly created ink/substrate interface to provide wetting during high speed printing.
U.S. Pat. No. 5,098,478 discloses water-based ink compositions comprising water, a pigment, a nonionic suifactant and a solubilizing agent for the nonionic surfactant. Dynamic surface tension in ink compositions for publication gravure printing must be reduced to a level of about 25 to 40 dynes/cm to assure that printability problems will not be encountered.
U.S. Pat. No. 5,562,762 discloses an aqueous jet ink of water, dissolved dyes and a tertiary amine having two polyethoxylate substituents and that low dynamic surface tension is important in ink jet printing.
U.S. Pat. No. 3,814,705 discloses the use of long chain 1,1-dialkyl ureas of the type R2NC(O)NH2 (R=alkyl group of C8 to C18) as foam suppressants in detergent compositions containing organic detergents, such as sulfate and sulfonate detergents, and alkaline builder salts.
Similarly, U.S. Pat. No. 3,691,082 discloses low-foaming rinsing, washing and cleaning compositions comprising (a) at least one compound having a cleaning or complexing action, (b) a foam-inhibiting isocyanurate and (c) an alkylated urea having at least eight substituents carbons on each of the urea nitrogens.
U.S. Pat. No. 2,708,183 discloses synthetic detergent compositions comprising a sulfated or sulfonated detergent and a minor amount of a higher alkyl substituted urea characterized by limited water-solubility.
U.S. Pat. No. 2,374,187 discloses non-allergenic toilet bars comprising sulfonated detergents and water-soluble, solid organic compounds which contain within the molecule the carboacylamido radical, e.g., ureas. The ureas are a significant amount of the final composition (50-95%).
U.S. Pat. No. 3,965,015 discloses bleach-stable fabric detergent and/or softening compositions comprising effective amounts of a urea represented by the formula: RNHCXNH(CH2)nNH2 where R is a C2-C18 alkyl group, X is oxygen or sulfur and n is 2-12.
U.S. Pat. No. 4,272,413 discloses softening and antistatic laundering compositions compatible with detergents comprising as the softening and antistatic agents short chain carbamoyl derivatives of long chain aliphatic amines, where the amino nitrogen is attached to a non-terminal or internal methylene group.
U.S. Pat. No. 2,335,862 discloses N,N-dibutylurea as a good solvent for rotenone in a non-aqueous herbicidal application.